Bricks are blocks or a single unit of a ceramic material used in masonry construction. It is essentially made from clay, lime-and-sand, concrete or shaped stone. Common methods in producing a brick comprises mixing the raw ingredients with water, pressing and fired to achieve strength. To obtain a consistent brick product, the bricks are often fired in tunnel kiln having conveyers, rails or kiln cars. Often, the composition of raw ingredients are adjusted to accelerate the burning process.
A China Patent No. CN101941825A has disclosed a manufacturing method of an environmental friendly brick from combustion slag of oil-bearing sludge. The method of manufacturing comprises mixing, extrusion molding in a mechanical vibration mode, steam-curing and cooling the produced brick naturally.
Another China Patent No. CN101913842A reveals a manufacturing method of a baked light-weight environmental friendly bricks prepared from paper mill sludge. The method comprises mixing the materials with water, extruding the damp product, molding with a blank cutter, pressing and naturally drying the for 7 days. Finally, the air-dried bricks are baked in a tunnel kiln for a finished product.
Nevertheless, the bricks in the prior arts above mainly comprises water, or a treatment using steam. This is due to the usage of cement which requires a hydration step to impart binding properties with other raw materials of a brick. Consequently, the brick is able to harden and solidify upon demoulding.
Geopolymer has been widely used as an alternative source of cement in brick making industry. Geopolymer bricks are essentially made from aluminosilicate material. In a highly alkaline environment, silicon hydroxides and aluminium hydroxides are released from the material. Subsequently, polycondensation reaction leads to solidification, whereby an aluminosilicate tetrahedral polymer network is formed. Recently, pozzolan or pozzolanic material has been gaining popularity to act as aluminosilicate material in an alkaline medium. Beside the choice of geopolymer material to be used, the ratio of each material, the homogeneity in the material mixture, the hardening or curing condition could also affect the integrity of the produced geopolymer brick.
A United States Patent No. US2012255462 A1 discloses a production of geopolymers from oil shale, mineral residues or a combination thereof. However, the prior art merely discloses the method of producing such geopolymer which comprises pretreatment of the oil shale, mixing, hardening and demoulding the geopolymer. The mixture is presented and also transported between stages in its slurry form until it reaches the hardening stage. Hence, more than a mould is necessary to hold the slurry before it is hardened. Further, a demoulding stage is required to retrieve the mould.
Nevertheless, most patented technologies emphasize on the composition and choice of geopolymer material in preparation of geopolymer. Hence, a system for batch production of geopolymer brick is desired to withstand high alkaline environment of geopolymer material.